This invention relates to high pressure fluid spraying equipment. In particular it relates to high pressure liquid spray and blasting equipment where liquid is emitted from a nozzle at pressures of the order of 1,000 to 10,000 pounds per square inch, but is operable at lower or higher pressures.
High pressure water equipment is typically operated by means of a gun having a "trigger" and connected by a hose to the reservoir and pump. When the trigger is released the pressure buildup in the hose can shatter the equipment unless an "unloader" valve is actuated so that the fluid under pressure will go to a bypass. Unloaders that have been previously described are unreliable, complex and costly. In particular, unloaders of the prior art frequently become gummed up and present a serious safety hazard.
It is typical of the unloader valves of the prior art to have a spring operated valve to open the bypass port. Thus, when the trigger controlling the nozzle of high pressure fluid spraying or blasting equipment is released, as is done intermittently during blasting and spraying operations, a large back pressure builds up against the pump until it pops the spring which has been holding the bypass port in closed position. The bypass valve springs are quickly rendered inoperative by these peaks of back pressure. Further, a minimum of constant flow through the bypass of 10% of unloader rated capacity is required.
One object of the present invention is to provide a safe and reliable combination regulator and unloader.
Other objects and advantages of this invention will be apparent from the description and claims which follow, taken together with the appended claims.